Toner Particle Core-Shell Design for Fixing and Storability
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Solution Overview
Problem
Electrophotographic toners face challenges with low-temperature fixability and heat-resistant storability, leading to issues like image streaking and fogging due to development member shaving and reduced cleaning performance, especially under high-speed and high-load printing conditions.
Innovation Solution
A toner composition featuring a core particle with a binder resin containing vinyl and polyester resins, or their hybrid, where the polyester resin has a cyclic structure and a high molecular weight fraction, and a thermosetting resin shell, with controlled average circularity to enhance deformation resistance and flowability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the softening temperature of the binder resin is reduced to achieve low-temperature fixability, then the fixing temperature is lowered, but the heat-resistant storability is reduced and toner-to-toner melt adhesion (blocking) occurs in high-temperature environments
Solution Approach 1:
The toner is divided into a core particle containing the binder resin and a shell layer containing a thermosetting resin. This segmentation allows the core to provide low-temperature fixability while the shell provides heat-resistant storability, resolving the contradiction between fixing temperature and heat-resistant storability.
Solution Approach 2:
The toner uses a composite structure combining a binder resin core with a thermosetting resin shell. The composite material approach allows the toner to exhibit both low-temperature fixability (from the binder resin) and heat-resistant storability (from the thermosetting resin shell), resolving the technical contradiction.
2Manufacturing precision
If the toner surface is made uneven to improve cleaning performance, then cleaning performance is enhanced, but flowability is reduced and fogging generation is facilitated
Solution Approach 1:
The shell layer is designed with local unevenness on its outer surface to improve cleaning performance, while the overall particle shape is maintained as substantially spherical to preserve flowability. This local quality approach allows cleaning performance enhancement without significant loss of flowability.
3Productivity
If the toner is used for extended high-speed image output, then productivity is increased, but development members are shaved by rubbing against protruded portions on the toner surface causing image streaking
Solution Approach 1:
The shell layer provides a locally optimized surface that reduces protrusions while maintaining cleaning performance, thereby reducing development member shaving and image streaking during extended high-speed operation.
Data Source
AI summary
The toner comprises a toner particle that comprises a binder resin-containing core particle and a thermosetting resin-containing shell on the surface of the core particle, wherein the binder resin includes at least one of (i) a vinyl resin and a polyester resin and (ii) a hybrid resin in which a vinyl resin and a polyester resin are bonded; the polyester resin comprises in a main chain thereof a cyclic structure, and the content of the polyester resin in the tetrahydrofuran-soluble matter of the toner is at least 51 mass%; the vinyl resin comprises a prescribed monomer unit; the thermosetting resin is at least one resin selected from melamine resins, urea resins, and oxazoline group-bearing vinyl resins; and the average circularity of the toner is in a prescribed range.